Is it true that committing a sin in Mecca is equivalent to 40,000 sins, and does this apply equally to residents, visitors, and pilgrims performing Umrah, and what must be done to expiate this sin?

Committing forbidden acts and sins within Allah's sacred precinct (Haram (definition)) is a greater and more severe transgression than committing them elsewhere. Even the mere intention to commit a sin in Makkah al-Mukarramah warrants severe punishment, as Allah Almighty says: "And whoever intends therein [to deviate] with wrongdoing – We will make him taste of a painful punishment." (22:25) The multiplication [of sin] is not in number but in the severity of the transgression, and this applies equally to residents, visitors, and those outside of it who merely intend a sin within it. If a Muslim errs in Makkah, they must hasten to sincere repentance.